1. Field of the Invention
Embodiments of the present invention generally relate to methods for automatically focusing a stereoscopic imaging device.
2. Description of the Related Art
Automatic focus, also referred to as auto focus, is an important feature of consumer imaging devices such as for example, digital still cameras, web cameras, digital video cameras, cellular telephones, and the like. The purpose of auto focus is to rapidly bring an object of interest in a scene into focus by moving the lens to the correct position such that the subject in a scene is in focus. A typical auto focus approach is a passive approach which uses image analysis to extract a measure of sharpness from focus regions in an image. The in-focus position of the lens is found by locating the maximum of a sharpness function computed from images of a scene captured at different lens positions.
Consumer imaging devices are now coming available that provide stereoscopic imaging. Performing automatic focus in a stereoscopic imaging device is challenging. A stereoscopic imaging device has two or more lenses, each with a separate image sensor. Further, the lenses are arranged such that each has a field of view of a scene that is slightly shifted from the other lenses. Because of the slight shift in perspective, if each lens is focused independently, each lens could end up focusing on different objects in the scene, resulting in poor image quality. Accordingly, the focusing of the lenses needs to be coordinated in some way so that each lens focuses on the same object.